Foxgloves produce a main blooming stalk and sometimes some smaller side stalks. If you remove just the tip of the stalk where the faded flowers are, meaning deadhead that central portion, the lower sidestalks will them develop and bloom. Basically, though, they only bloom once. Also, this plant is usually biennial. This means it grows the first year, overwinters, blooms the second year, and then dies. If you want to have an ongoing supply of foxgloves you need to replant or else allow them to set seed and then allow a few seedlings to come along to replenish the patch.